Source: The illustration above and text below are from Harper's Weekly, March 29, 1862, page 203.

The "Monitor"

To the views which we have before given of the Monitor we now add three plans. They give a more perfect idea of her construction than any thing which has been published. Figure 1 represents her as launched and ready for action; Figure 2 is a plan of her deck; and Figure 3 is a cross section cut down through the turret. The black line in Figure 1 above the water-line shows precisely how much of her body appears above the water.